private ControlFlowGraph(ZRoutine routine)
{
this.routine = routine;
this.entry = new Block(isEntry: true);
this.exit = new Block(isExit: true);
var instructions = new InstructionLinkedList(routine);
this.codeBlocks = new List <CodeBlock>(BuildGraph(instructions));
}
private SortedSet <int> CollectJumpTargets(InstructionLinkedList instructions)
{
var results = new SortedSet <int>();
var node = instructions.First;
// the first instruction is a jump target of the entry block.
results.Add(node.Value.Address);
while (node != null)
{
var instruction = node.Value;
if (instruction.HasBranch)
{
// conditional branch
if (instruction.Branch.Kind == BranchKind.Address)
{
var address = instruction.Address + instruction.Length + instruction.Branch.Offset - 2;
results.Add(address);
}
// add "else" portion of conditional (i.e. the next instruction).
if (node.Next != null)
{
results.Add(node.Next.Value.Address);
}
}
else if (node.Value.Opcode.IsJump)
{
// unconditional jump
var address = instruction.Address + instruction.Length + (short)instruction.Operands[0].Value - 2;
results.Add(address);
}
node = node.Next;
}
return(results);
}
private List <CodeBlock> BuildGraph(InstructionLinkedList instructions)
{
var jumpTargets = CollectJumpTargets(instructions);
var results = new List <CodeBlock>(jumpTargets.Count);
var codeBlocks = new Dictionary <int, CodeBlock>(jumpTargets.Count);
foreach (var jumpTarget in jumpTargets)
{
var codeBlock = new CodeBlock(jumpTarget);
results.Add(codeBlock);
codeBlocks.Add(jumpTarget, codeBlock);
}
var node = instructions.First;
var currentBlock = codeBlocks[node.Value.Address];
this.entry.AddJumpTarget(currentBlock);
while (node != null)
{
var instruction = node.Value;
if (codeBlocks.ContainsKey(instruction.Address))
{
currentBlock = codeBlocks[instruction.Address];
}
if (currentBlock != null)
{
currentBlock.AddInstruction(instruction);
instructionCount++;
if (instruction.HasBranch)
{
// conditional branch
switch (instruction.Branch.Kind)
{
case BranchKind.Address:
var address = instruction.Address + instruction.Length + instruction.Branch.Offset - 2;
var blockAtAddress = codeBlocks[address];
currentBlock.AddJumpTarget(blockAtAddress);
break;
case BranchKind.RFalse:
case BranchKind.RTrue:
currentBlock.AddJumpTarget(exit);
break;
}
// add "else" portion of conditional (i.e. the next instruction).
if (node.Next != null)
{
var blockAtAddres = codeBlocks[node.Next.Value.Address];
currentBlock.AddJumpTarget(blockAtAddres);
}
// done with this block
currentBlock = null;
}
else if (instruction.Opcode.IsJump)
{
// unconditional jump
var address = instruction.Address + instruction.Length + (short)instruction.Operands[0].Value - 2;
var blockAtAddress = codeBlocks[address];
currentBlock.AddJumpTarget(blockAtAddress);
// done with this block
currentBlock = null;
}
else if (instruction.Opcode.IsReturn || instruction.Opcode.IsQuit)
{
currentBlock.AddJumpTarget(exit);
// done with this block
currentBlock = null;
}
}
else
{
Debug.WriteLine("Unreachable code encountered at: " + instruction);
}
node = node.Next;
}
return(results);
}
